---
title: "Platform concepts"
description: "Blocks, pages, apps, publications, and the remix lineage: the vocabulary the whole platform is built on."
---

> Documentation Index
> Fetch the complete documentation index at: https://docs.murl.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Platform concepts

Everything on murl reduces to a small set of nouns. This page defines them
once; the rest of the docs use them without re-explaining.

## Blocks

A **block** is one model-backed generation step: a prompt, a model, typed
inputs, and an output (text, image, or video). Blocks are the atoms of the
studio:

- **Chaining**: a block's output can feed the next block's input (text to
  image to video), including typed media sockets: image-to-video, and
  audio/video inputs for lip-sync and add-sound workflows.
- **Priced upfront**: every block shows its posted credit price before it
  runs; chained steps whose cost depends on earlier outputs (e.g. video
  duration) are re-quoted from resolved inputs.
- **Model-agnostic**: a block binds to a model from the
  [registry](/models); swapping the model keeps the block.

## Pages

A **page** is a published studio document: blocks arranged in a Notion-style
editor, shipped as a runnable surface at `/p/{id}`. Visitors run the page with
their own inputs and remix it in one click; running and remixing live in one
place. Pages are the fast path from idea to published, earning work: no code,
no design decisions beyond the blocks themselves.

## Apps

An **app** is a custom AI product with full UI freedom: a single-module worker
that a creator vibe-codes through the authoring agent, served in a sealed
sandbox at `/apps/{id}`. Apps talk to the platform exclusively through the
[`env.MURL` SDK](/sdk) for models, chains, storage, and uploads, and inherit
wallets, pricing, history, and creator attribution with zero code. See
[Custom apps](/apps).

## Publications

Publishing a page or an app creates a **publication**, the marketplace unit
that carries title, cover media, category, pricing surface, and lineage. One
column discriminates the two kinds: `format = 'page' | 'app'`. The marketplace,
search, and profile surfaces are lenses over publications.

## Remix lineage

Every remix records its parent. That produces a **lineage tree** per
publication, and the [creator pool](/economics) pays *up the tree*: a
foundational page or app earns from the runs of every derivative that
descends from it, with harmonic decay by depth. Remixing is therefore not a leak of value;
it is the compounding mechanism.

## Wallets and credits

Users hold a wallet; actions cost **credits** (1 credit = $0.01). Internally
every amount is integer **micros** ($1 = 1,000,000 micros) on an append-only
ledger; credits are a display skin at the UI edge, never a unit of internal
math. Every spend follows **hold, run, settle**: the quote is held before
the provider is called, the actual cost settles after, and a failed provider
call releases the hold.

Source: https://docs.murl.ai/platform/index.mdx